JSFiddle - React, Tailwind, and code Playground

JavaScript

var myVar = phoneCheck('a3','a2','o3','o1');
console.log(myVar);


function phoneCheck(newCell,newHome,oldCell,oldHome) {
  
  

  var TnewCell = newCell.replace( /\D+/g, ''); //extractNumbers(newCell);
  var ToldCell = oldCell.replace( /\D+/g, '');//extractNumbers(oldCell);
  var TnewHome = newHome.replace( /\D+/g, '');//extractNumbers(newHome);
  var ToldHome = oldHome.replace( /\D+/g, '');//extractNumbers(oldHome);
  
  
  if (TnewCell === ToldCell) {
    return TnewCell;
  } else if (TnewCell === ToldHome && TnewHome === ToldCell) {
    return ToldCell;
  }
  
  if (TnewCell === '' && ToldCell !== '' ) {
    return ToldCell;
  }
  
  if (TnewCell !== ToldCell && TnewCell !== ToldHome) {
   return TnewCell;
  }
  
  return "No value found";
  
  function xNum (tInput) {
    return tInput.replace( /\D+/g, '');
    }

}

function sleep(milliseconds) {
  var start = new Date().getTime();
  for (var i = 0; i < 1e7; i++) {
    if ((new Date().getTime() - start) > milliseconds){
      break;
    }
  }
}